1. Field of the Invention
The present invention relates to a retaining device, and more particularly to a retaining device for securing a heat sink to an electronic package such as a central processing unit (CPU).
2. Description of Related Art
With the rapid development of electronics technology, electronic devices such as CPUs are able to process signals at unprecedented high speeds. As a result, CPUs can generate copious amounts of heat. The heat must be efficiently removed from the CPU; otherwise, abnormal operation or damage may result.
Conventionally, a heat sink is attached on a CPU by various types of clips. A popular conventional clip comprises a pressing portion for pressing the heat sink, and a pair of resilient portions extending from opposite ends of the pressing portion. A pair of arms depends from opposite ends of the resilient portions, for engaging with corresponding protrusions mounted at a periphery of the CPU. The heat sink is thus attached on the CPU. However, when the assembly is subjected to vibration or shock during normal use, the heat sink is liable to be horizontally displaced relative to the CPU. This disturbs thermal contact between the heat sink and the CPU. Therefore, the efficiency of heat removal is diminished.
Accordingly, an object of the present invention is to provide a retaining device for a heat sink which firmly attaches the heat sink to an electronic package such as a CPU and prevents the heat sink from moving horizontally relative to the electronic package.
In order to achieve the object set out above, a retaining device in accordance with a preferred embodiment of the present invention is for attaching a heat sink to a CPU mounted on a circuit board. The retaining device comprises a pair of clips, a backplate, and four pins. Each clip comprises a central pressing portion, two resilient portions extending from opposite ends of the pressing portion, two shoulders extending horizontally from free ends of the resilient portions, and two arms depending from free ends of the shoulders. Each shoulder defines a circular first cutout, and a circular second cutout smaller than and in communication with the first cutout. The backplate defines four holes in four corners thereof. Each pin forms a blocking head at a top end thereof, and a blocking stop at a bottom end thereof. The pins are sequentially extended through the backplate, the circuit board and the heat sink. The heads are initially received through the first cutouts, and then engaged on the shoulders at the second cutouts. The heads press downwardly on the clips, and the stops press upwardly on the backplate. Thus, the clips and the backplate firmly sandwich the heat sink, the CPU and the circuit board therebetween. Good thermal contact between the heat sink and the CPU is thereby attained, for high heat removal efficiency.
Other objects, advantages and novel features of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: